AIX Version 4.3 Differences Guide

• Separate Specular Color
Lighting calculations are modified to produce a primary color consisting of
emissive, ambient, and diffuse terms of the usual GL lighting equation, and a
secondary color consisting of specular terms. Only the primary color is
modified by the texture environment; the secondary color is added to the
result of texturing to produce a single post-texturing color. This allows
highlights whose color is based on the light source creating them, rather than
the surface properties.
• Texture Coordinate Edge Clamping
GL normally clamps such that the texture coordinates are limited to exactly the
range [0,1]. When a texture coordinate is clamped using this algorithm, the
texture sampling filter straddles the edge of the texture image, taking half its
sample values from within the texture image, and the other half from the
texture border. It is sometimes desirable to clamp the texture without requiring
a border, and without using the constant border color.
A new texture clamping algorithm, CLAMP_TO_EDGE, clamps texture
coordinates at all mipmap levels such that the texture filter never samples a
border texel. The color returned when clamping is derived only from the edge
of the texture image.
• Texture Level of Detail Control
Two constraints related to the texture level of detail parameter λ (lambda) are
added. One constraint clamps λ (lambda) to a specified floating point range.
The other limits the selection of mipmap image arrays to a subset of the arrays
that would otherwise be considered.
Together, these constraints allow a large texture to be loaded and used initially
at low resolution and to have its resolution raised gradually as more resolution
is desired or available. Image array specification is necessarily integral rather
than continuous. By providing separate, continuous clamping of the λ
(lambda) parameter, it is possible to avoid popping artifacts when higher
resolution images are provided.
• Vertex Array Draw Element Range
A new form of DrawElements that provides explicit information on the range of
vertices referred to by the index set is added. Implementations can take
advantage of this additional information to process vertex data without having
to scan the index data to determine which vertices are referenced.
Because OpenGL 1.2 is a superset of OpenGL 1.1, all programs written for
OpenGL 1.1 run on OpenGL 1.2 without modification, recompiling, or relinking.
OpenGL 1.2 support is available in AIX 4.3.2 only on the GXT3000P PCI
Graphics Accelerator. Users of other graphics adapters are limited to functions
contained in OpenGL 1.1 and OpenGL 1.1 extensions. The optional Imaging
Extension subset is not supported by the IBM OpenGL 1.2 implementation (at this
time).
The ZAPdb interactive OpenGL debugger is enhanced to support all new features
provided in OpenGL Version 1.2.
Graphical Environment Enhancements 229